1. Field of the Invention
The present invention relates generally to devices for reducing the severity of injury to a pedestrian struck by an automotive vehicle, and more particularly to an impact energy management device for mounting to the front bumper of a vehicle that exhibits a relatively soft response to a localized impact from a pedestrian""s leg, and a relatively stiff response to a broad impact from another vehicle.
2. Background
It is desirable for a front bumper of a vehicle to be designed so that a collision of the vehicle with a pedestrian will result is as little injury to the pedestrian as is practical. The objective of minimizing pedestrian injury is complicated, however, by the requirement that the front bumper and related vehicle structure be able to protect vehicle occupants during a high-energy impact with another vehicle or a fixed object by effectively absorbing impact energy. The bumper must also be resistant to damage during a low-energy collision in order to reduce repair costs. Packaging constraints driven by styling and other factors may also affect the ways in which these three objectives may be met.
The most common way to address these conflicting requirements has been to provide a relatively stiff bumper beam designed to manage a high-energy (vehicle-to-vehicle or vehicle-to-barrier) impact, and position a relatively soft material or structure in front of the bumper beam. The soft material or structure deforms in a pedestrian impact to provide injury-reducing cushioning, but typically contributes only a negligible amount of energy absorption during a high-energy collision. One disadvantage to this conventional solution is that the vehicle front-end must be longer in order to package these systems in series.
The present invention provides an energy absorbing device for pedestrian safety that has a first, relatively low-resistance mechanical response when struck by an object having the approximate width of a human leg, and a second, relatively high-resistance response when struck by an object wider than a human leg. The device is primarily intended to be mounted to the front bumper beam of a vehicle, but may be mounted on any exterior surface that may contact a pedestrian during a collision.
According to the invention, the impact energy management device comprises a backplate attachable to an exterior of the vehicle and a plurality of seesaw elements, each seesaw element attached to the backplate at a pivot point for pivoting movement relative to the backplate and having first and second contact ends spaced from the beam. When only one end of a seesaw element is urged toward the backplate by a collision with a pedestrian""s leg, the seesaw element pivots with respect to the backplate. The pivot point is designed to absorb energy as the pivoting action takes place and offer a relatively low resistance to intrusion of the leg toward the backplate as it does so. When a wider object strikes the device, both contact ends of a seesaw element are engaged so that the element bends toward the backplate. The strain caused by the bending offers a higher resistance to intrusion by the object.
According to another feature of the invention, the seesaw elements are arranged in at least two generally horizontal rows, and adjacent rows are offset from one another in a horizontal direction such that the contact ends of seesaw element adjacent rows are not in vertical alignment with one another. This configuration ensures that a pedestrian leg will be engaged by the contact end of at least one element no matter where on the device the leg strikes.
According to the preferred embodiment of the invention disclosed herein, at least one of the seesaw elements is shaped like a V, with the pivot point located at a vertex of the V and the contact ends located at opposite ends of the V. The first and second contact ends are separated from one another by a horizontal distance somewhat greater than the expected width of a pedestrian leg. This ensures that in a collision with a pedestrian leg, the leg will only engage one of the contact ends of any of the seesaw elements so that the desired pivoting movement occurs.
Other features and advantages of the present invention will be readily appreciated and better understood after reading the subsequent description when considered in connection with the accompanying drawings.